Exercise board



FIG. 1 is a first perspective view of an exercise board;

FIG. 2 is a second perspective view thereof;

FIG. 3 is a side elevation view thereof;

FIG. 4 is a bottom plan view thereof;

FIG. 5 is a top plan view thereof;

FIG. 6 is a front elevation view thereof; and,

FIG. 7 is a back elevation view thereof.

The broken lines illustrate portions of the exercise board which form no part of the claimed design. 

The ornamental design for an exercise board, as shown and described. 